to him, as his erroneous marriage to her sister is considered licentious sexual relations, and one who has intercourse with his wife’s relatives has not rendered his first wife forbidden to himself. And he is permitted to the relatives of the second woman, e.g., her daughter, and this second woman is permitted to his relatives, e.g., his son, as the marriage was entirely invalid. And if the first woman died he is permitted to the second woman, despite the fact that he has already engaged in forbidden relations with her.

If they said to him that his wife is dead, and he married her sister, and afterward they said to him that she was alive when he married the sister and only later died, in this case the first child, born to the sister while his wife was still alive, is a mamzer, as he was born from the union of a man and his sister-in-law, and the last one is not a mamzer. Rabbi Yosei says: Whoever disqualifies others also disqualifies himself, and whoever does not disqualify others does not disqualify himself either. Rabbi Yosei’s obscure statement will be explained by the Gemara.

GEMARA: With regard to the case of a man who married his wife’s sister after he was informed that his wife was dead, the Gemara comments: And even if his wife and his brother-in-law both went overseas and he was told that they had died, the halakha is that this marriage he performed is effective only to the extent that his brother-in-law’s wife is forbidden to his brother-in-law. The reason for this prohibition is that he performed a marriage ceremony with a married woman by mistake, and one who erroneously weds a married woman has thereby rendered her forbidden to her husband. The Gemara adds: Even so, it is only his brother-in-law’s wife who is forbidden to her husband, whereas his own wife remains permitted to him.

It might have been thought that his own marriage, which caused this to be an act of forbidden sexual relations, would also be adversely affected. But the Gemara adds that we do not say: Since his brother-in-law’s wife is forbidden to his brother-in-law, his wife is likewise forbidden to him. The Gemara suggests: Let us say that the mishna is not in accordance with the opinion of Rabbi Akiva. The reason is that if the mishna follows the opinion of Rabbi Akiva, his wife is now considered, with regard to him, the sister of his divorcée.

As it is taught in a baraita: None of those with whom relations are forbidden by Torah law require a bill of divorce from him, even if he married them in a proper manner, apart from a married woman who married by mistake by permission of the court. And Rabbi Akiva adds: Also a brother’s wife and a wife’s sister. Since it is possible that these two women could become permitted to him, by levirate marriage in the case of a brother’s wife, or a wife’s sister after his wife’s death, they too require a bill of divorce. And with regard to the issue at hand, since Rabbi Akiva said that a wife’s sister requires a bill of divorce, this factor by itself indicates that his wife is forbidden to him, as his wife is considered the sister of his divorcée.

The Gemara refutes this claim: And wasn’t it stated with regard to this case that Rav Giddel said that Rav Ḥiyya bar Yosef said that Rav said: In the case of this brother’s wife, mentioned by Rabbi Akiva, what are the circumstances? For example, if his brother betrothed a woman and then went overseas, and the man who was here heard that his brother was dead, and he arose and married his brother’s wife as a yevama. The reason for Rabbi Akiva’s ruling is that uninformed people will say: This first one had a condition in the betrothal with his wife, and his betrothal was canceled because the condition was left unfulfilled, and this other one married well, in compliance with the halakha, as she was not his brother’s wife. It is for this reason that Rabbi Akiva requires him to give her a bill of divorce.

And in this case of a wife’s sister as well, what are the circumstances? For example, if he betrothed a woman and she went overseas, and he heard she died and arose and married her sister. As people will say: This first one, he had a condition in her betrothal, and as the condition was not fulfilled the betrothal is annulled, and this other one married well. However, with regard to the case of the mishna, which involves an actual previous marriage, can it be said that he had a condition in the marriage? There is a presumption that no man marries a woman conditionally. Once he marries her, it is assumed that he waived all prior conditions, and therefore even Rabbi Akiva agrees that a bill of divorce is not required in this case.

Rav Ashi said to Rav Kahana: If it is the opinion of Rabbi Akiva, let him also teach the case of his mother-in-law, as she is another forbidden woman who nevertheless requires a bill of divorce, as we have heard him, Rabbi Akiva, say: One who has relations with his mother-in-law after his wife’s death is not liable to being executed by burning, because the prohibition lapses upon his wife’s death.

As it is taught in a baraita: The Torah states, with regard to one who takes a woman and her daughter: ''They shall be burned in fire, he and they [et’hen]'' (Leviticus 20:14). Now this cannot literally mean that both women are burned, as the first woman he took did not sin at all. The Sages therefore explained that the word et’hen means he and one of them [mehen]. This is the statement of Rabbi Yishmael. Rabbi Akiva says: He and both of them. Since it is hard to understand how they could both deserve punishment, the amora’im suggested various interpretations of Rabbi Akiva’s opinion.

Granted, this makes sense according to the explanation of this dispute suggested by Abaye, who said that the interpretation of the meaning of the verse is the difference between them. In other words, Rabbi Yishmael and Rabbi Akiva did not argue over the halakha itself, but merely over the manner in which the halakha is derived from the Torah. That is, Rabbi Yishmael holds that it states: One woman, and the plain meaning of the verse is: He and one of them. And Rabbi Akiva holds that it states: Two, e.g., if he took two women who were both forbidden to him, such as his mother-in-law and her mother, they are both liable to be executed by burning. If this is the dispute between Rabbi Akiva and Rabbi Yishmael, it is fine, as there is no proof from here that the prohibition of a mother-in-law lapses upon his wife’s death.

However, there is a difficulty according to the explanation of Rava, who said that the practical difference between Rabbi Yishmael and Rabbi Akiva’s opinion concerns one’s mother-in-law after his wife’s death. Rabbi Yishmael maintains that even after the death of one’s wife he is liable for marrying his mother-in-law. Rabbi Akiva maintains that one is liable only if both women are alive, as the verse mentions two women, but if the first one has already died his relations with the second woman are no longer punishable by Torah law. If so, let the tanna of the mishna, according to Rabbi Akiva, also teach that one must give a bill of divorce to his mother-in-law whom he married by mistake, as she too will be permitted to him after his wife’s death.

Rav Kahana said to Rav Ashi: Granted that the verse excluded her from the punishment of burning, did the verse also exclude her from a prohibition? Even Rabbi Akiva agrees that the Torah prohibits a man from marrying his mother-in-law after his wife’s death. Consequently, he cannot marry her in a permitted manner, despite the fact that according to Rava’s explanation Rabbi Akiva maintains that they are not executed by burning.

§ The Gemara asks another question, from a different perspective: And let his wife be forbidden by his sexual relations with her sister, just as it is in the case of a woman whose husband went overseas, who is forbidden to her husband if she had relations with another man by mistake. The Gemara answers: This is not comparable. With regard to his wife, who is forbidden to him by Torah law if she committed adultery intentionally, the Sages decreed concerning her that she is forbidden to him even if she did so unwittingly.